Bubble Elephant is a large elephant-shaped bubble character who debuts in the episode "Bubblestand" and is seen again in "Spot Returns."
In "Bubblestand," when SpongeBob is showing Patrick various bubbles from his technique, he uses two hands on his bubble wand to create this elephant bubble. Patrick mistakes it for a giraffe and is laughing until the bubble ends up blowing inside of Squidward's house. The bubble then pops into a bunch of miniature bubbles, making a loud elephant trumpet noise. Squidward then confronts SpongeBob and Patrick about the bubble stand.
In "Spot Returns," SpongeBob blows this bubble before noticing Plankton painting a sign next to the Chum Bucket.